The present invention relates to an image forming apparatus in which an image can be obtained in such a manner that: a toner image is formed on an image carrier by means of electrophotography; and the formed toner image is transferred onto a transfer sheet. The present invention more particularly relates to an image forming apparatus such as a printer, copier and facsimile in which a process cartridge including an image carrier on which an electrostatic latent image is formed, and a developing unit are detachably provided.
As the size of an image forming apparatus such as a printer and copier has been made small, and its function has been improved, the structure of the image forming apparatus has become highly precise and complicated.
Recently, an image forming apparatus having a process cartridge in which an image carrier and at least one of a developing means and a cleaning means are integrated into one unit, has been developed so that an operator can maintain the apparatus easily.
In the case of an image forming apparatus such as a printer and a copier having a process cartridge, when an image carrier provided in the process cartridge is consumed or deteriorated, the process cartridge itself is replaced with a new one, so that an operator can maintain the image forming apparatus without any expertise. In the apparatus described above, the apparatus is provided with a guide member by which the process cartridge can be guided, and all the operator must do is to insert the process cartridge into the apparatus along the guide member.
In a conventional image forming apparatus, the direction of process cartridge removal and that of transfer sheet movement make a right angle with each other, so that the work of process cartridge removal is troublesome and complicated, and further the space to install the image forming apparatus is restricted. Furthermore, a wide space is required to maintain the apparatus.
In order to solve the aforementioned conventional problems, an image forming apparatus disclosed in the official gazette of the Japanese Patent Publication Open to Public Inspection No. 279870/1986 has been proposed in the apparatus disclosed in the aforemention official gazette, the direction of the transfer sheet movement agrees with the direction of process cartridge removal, so that the parts can be easily replaced and the operation can be conducted easily, and further, the working space is not restricted.
However, in the case of the image forming apparatus disclosed in the official gazette of the Japanese Patent Publication Open to Public Inspection No. 279870/1986, the process cartridge is replaced in such a manner that: the upper housing of the apparatus is opened, and the operator must pull the process cartridge from the apparatus and then take it out. Therefore, the work is very hard for the operator when the process cartridge is large and heavy.
In the aforementioned conventional embodiment, the process cartridge is attached to and detached from the apparatus body under the condition that the upper housing is opened. Therefore, it is troublesome to attach the process cartridge to the apparatus body and it is also troublesome to detach it from the apparatus body.
Especially, in the case of a process cartridge in which an image carrier, a charging unit, and a plurality of developing units are provided, in general, the developing units are made separately from the process cartridge, so that it is difficult to assemble the developing units to the cartridge accurately and stably. Since she developing units are driven, it is necessary to maintain strength and accuracy. Therefore, the structure of the developing units necessarily becomes complicated. Further, the shape and structure of the process cartridge in which the developing units are provided, are complicated, so that there is a problem to maintain its mechanical strength. In order to maintain its accuracy, the number of parts of the process cartridge is increased so that the cost is inevitably raised. When accuracy of a process cartridge is not sufficiently high in the case of a color image forming apparatus, maintainability is deteriorated, so that color balance can not be sufficiently adjusted.
Further, the present invention relates to a process cartridge to be detachably provided to a printer, a copier or a facsimile, in which an image forming means including an image carrier on which an electrostatic latent image is formed, and including a developing unit which develops the electrostatic latent image so that a toner image can be formed, is integrated into one unit, and more particularly relates to a developer supply method which is used when new developer is supplied to the inside of the aforementioned developing unit.
When the aforementioned process cartridge is assembled or after it has been assembled, new developer is loaded into the developing tank of the process cartridge. Developer is loaded into the developing tank of the aforementioned process cartridge in such a manner that: members provided in the upper portion of the developing unit, for example, a cover of the apparatus and an image carrier, are removed; further an upper lid provided on the upper portion of the developing unit is removed so that the developing tank is opened; developer is loaded into the tank; and the tank is closed and fixed by the upper cover.
Since the above-described complicated work must be done, the following problems are caused: assembling efficiency of the process cartridge is lowered; and developer is scattered and the apparatus is stained by the scattered developer when developer is loaded.
Especially, in the case of a color image forming apparatus, the process cartridge is provided with a plurality of developing units, so that the aforementioned problems are frequently caused.
In an electrophotographic type of image forming apparatus such as a monocolor type of analog copier and a copier or a printer in which a semiconductor laser and LED is used, the following image forming apparatus is proposed: in order to replace a photoreceptor or supply developer carrier and toner, an essential portion of the image forming apparatus is integrated into a unit so that the unit can be taken out from the apparatus for maintenance. Various structures are proposed in which a transfer sheet passage is opened in order to remove a jammed transfer sheet from the apparatus.
A typical structure of the aforementioned image forming apparatus has been disclosed in the official gazette of Japanese Patent Publication No. 54392/1983, in which a photoreceptor drum, a developing unit and a cleaner are integrally mounted on a support member so that they can be easily withdrawn from the apparatus for replacement and maintenance of the aforementioned units. An image forming apparatus in which the aforementioned units are integrated into one disposable unit, has been disclosed in the official gazette of Japanese Patent Publication Open to Public Inspection No. 154255/1982. A printer in which the same disposable cartridge as described above is used, and in which a latent image is formed on a photoreceptor drum by an exposure scanning writing system using a semiconductor laser, has been disclosed in the official gazette of Japanese Patent Publication Open to Public Inspection No. 147366/1984. In these official gazettes, the structure is disclosed in which an upper housing is opened so that a jammed transfer sheet can be removed from a transfer sheet passage. According to the aforementioned official gazette of Japanese Patent Publication Open to Public Inspection No. 154255/1982, a disposable process cartridge is detachably provided to an upper housing which is composed of two portions, so that the cartridge can be replaced quickly and a jammed paper can be removed easily. According to the official gazette of Japanese Patent Publication Open to Public Inspection No. 1161/1983, a housing is composed of two portions in order to improve workability of cartridge replacement, and a process cartridge is detachably provided to the lower housing so that maintainability can be improved. According to the official gazettes of Japanese Patent Publication Open to Public inspection Nos. 244058/1988, 244059/1988, 244064/1988, and 179168/1989, a vertical type of process cartridge has been disclosed, wherein units are vertically arranged so that the operation can be performed from one side and jam clearance can be performed effectively.
However, in order to detach the process cartridge from the apparatus body, the housing must be composed in such a manner that it can be split, and at the same time the gears of a drive system to drive a photoreceptor and developing unit must be positively engaged with each other when the cartridge is attached to the apparatus, and disengaged when the cartridge is detached from the apparatus. Accordingly, the structure becomes complicated, and further its operation is not simple.
Further, the present invention relates to a color image forming apparatus such as a printer, copier and facsimile in which a process cartridge including an image carrier on which an electrostatic latent image is formed, and a plurality of developing units to develop the electrostatic latent image to form a color toner image, is detachably provided to the apparatus body, and more particularly relates to supply of color developer to a developing unit installed in the aforementioned process cartridge.
There is a possibility that a wrong color developer is loaded into a developer tank when a color developer is loaded before a new process cartridge is assembled to the aforementioned color image forming apparatus.
When the developer is loaded into the developing tank, the cover of the process cartridge and the image carrier must be removed, and further the upper lid of the developing unit must be removed so that the developing tank can be opened. After the developer has been loaded, the aforementioned members must be assembled and fixed so that the loaded developer can be securely enclosed. Accordingly, much labor is required to assemble the image forming apparatus, and workability is lowered. Furthermore, the following problems are caused: when a developer is loaded, it scatters and stains surrounding units and the apparatus floor; and the operator body and clothes may become stained.
When a new image forming apparatus is delivered from a factory, the aforementioned process cartridge for forming a color image having a plurality of developing units is not loaded with developer, so that adjustment of color balance can not be conducted since print output can not be obtained from the process cartridge. Therefore, quality of the apparatus can not be guaranteed.